The veterinarians, from the University of Melbourne, said Phalaris aquatica -- a common pasture crop in central Victoria -- have caused the suffering among eastern gray kangaroos, the Guardian reported. Wildlife officials said the kangaroos were suffering from Phalaris “staggers,” which is common among sheep and cattle that graze in Australia.

“A kangaroo with full-blown toxicity is just horrible,” Manfred Zabinskas from Five Freedoms Animal Rescue told Guardian Australia. “Their head flies around like they have got a broken neck; they summersault; they crash into fences and trees … they look like they are drunk.”

Phalaris, also known as canary grass, is a tall grass common to southeastern Australia. Some farmers have avoided planting the species because the “staggers” can cause heart failure among animals, the Guardian reported.

In domestic animals, the condition can be controlled by adding copper into their diet. But in kangaroos, the condition is believed to be irreversible, the Guardian reported.